Resin surface hydrophilization method, plasma processing device, laminate body, and laminate body manufacturing method

ABSTRACT

[Problem] 
     To provide a laminate body in which a resin base member and a metal deposition film are brought into firmly close contact with each other. 
     [Solution] 
     The laminate body manufacturing method includes a desorption step S 10 , an introduction step S 20 , a deposition step S 30 , and a coating step S 40 . In the desorption step S 10 , a hydrophobic surface of resin is irradiated with plasma to desorb at least some of the atoms constituting the resin from the surface. In the introduction step S 20 , the surface of the resin subjected to the desorption step S 10  is irradiated with hydroxyl radicals to introduce a hydroxyl group onto the surface of the resin. In the deposition step S 30 , a metal film is deposited on the surface of the resin subjected to the introduction step S 20 . In the coating step S 40 , the surface of the metal film is coated with a metal layer formed of the same metal as the metal forming the metal film.

FIELD

The present application relates to a resin surface hydrophilizationmethod, a plasma processing device, a laminate body, and a laminate bodymanufacturing method, which are applicable to manufacturing a circuitsubstrate capable of handling millimeter waves or microwaves with asmall transmission loss.

BACKGROUND

As a base member of a circuit substrate, a low-dielectric liquid crystalpolymer (LCP) or a low-dielectric fluororesin such aspolytetrafluoroethylene (PTFE) has begun to be used instead ofconventional polyimide. There is a problem that LCP or PTFE has pooradhesion to copper used as a wire material. For this reason, the surfaceof the base member of the circuit substrate is chemically roughened, orunevenness is formed on the surface of copper foil which is to bebrought into close contact with the substrate, thereby improving thedegree of physical adhesion between the substrate and copper.

When copper is formed on the surface of the base member by chemicallyroughening the surface of the base member, the transmission loss of thecircuit substrate increases due to roughness of the surface of the basemember. When copper is attached to the surface of the base member usingan adhesive, the adhesive layer itself causes transmission loss of thecircuit substrate. When copper is formed on the surface of the basemember by plating, sufficient adhesion between the base member andcopper cannot be obtained. There is also a method of obtaining alaminate body of a PTFE base member and copper by irradiating the PTFEbase member with atmospheric plasma to activate the surface thereof,replacing fluorine in the PTFE base member with a hydroxyl group derivedfrom moisture in the air, and bringing copper into close contact withthe surface of the PTFE base member.

However, even when the PTFE base member is irradiated with atmosphericplasma, the contact angle of PTFE base member with water is about 50°.Then, when copper is brought into close contact with the surface of thePTFE base member, the degree of adhesion between the PTFE base memberand copper is about 0.4 N/mm. Therefore, in the process of producing acircuit pattern of copper on the PTFE base member, there is a fear thatcopper is peeled off from the PTFE base member. In addition, when heatis applied to the PTFE base member in a circuit-pattern manufacturingprocess, the degree of adhesion between the PTFE base member and copperfurther decreases. Further, since the time during which the surface ofPTFE base member is modified is about 24 hours, it is necessary toquickly bring copper into close contact with the surface of the PTFEbase member, which has been a constraint on manufacturing circuitsubstrates.

In Patent Document 1, the surface of a base member is cleaned with ahigh energy beam in a vacuum, and then, the surface of the base memberis irradiated with ionized water vapor to adsorb a hydroxyl group on thesurface of the base member. However, since the energy of the ionizedwater vapor is strong, the hydroxyl group once adsorbed is desorbedagain from the surface of the base member when the surface of the basemember is irradiated with ions of other water vapor. Therefore, thecontact angle of the surface of the base member with water is about 40°.

LIST OF DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Patent Application Publication No.    H9-3220

SUMMARY Technical Problem

In view of such circumstances, it is an object of the presentapplication to provide a resin surface hydrophilization method forimparting high hydrophilicity to a hydrophobic surface of resin for along period of time, a plasma processing device capable of performingthe resin surface hydrophilization method, a laminate body manufacturingmethod using the resin surface hydrophilization method, and a laminatebody obtained by, for example, the laminate body manufacturing method.

Solution to Problem

A resin surface hydrophilization method of the present applicationincludes a desorption step of desorbing at least a part of atomsconstituting resin from a hydrophobic surface of the resin byirradiating the surface with plasma, and an introduction step ofintroducing a hydroxyl group on the surface of the resin subjected tothe desorption step by irradiating the surface of the resin withhydroxyl radicals.

A laminate body manufacturing method of the present application includesa desorption step of desorbing at least a part of atoms constitutingresin from a hydrophobic surface of the resin by irradiating the surfacewith plasma, an introduction step of introducing a hydroxyl group on thesurface of the resin subjected to the desorption step by irradiating thesurface of the resin with hydroxyl radicals, and a deposition step ofdepositing a metal film on a surface of the resin subjected to theintroduction step.

A plasma processing device of the present application includes a firstprocessing device including a first chamber, a first holding unit whichholds resin, a first gas introduction unit which introduces, into thefirst chamber, first gas for desorbing at least a part of atomsconstituting the resin from a surface of the resin when turned intoplasma, and a first plasma generation unit which turns the first gasinto plasma; and a second processing device including a grounded secondchamber, a second holding unit which holds the resin processed in thefirst chamber and to which a first DC voltage is applied, a second gasintroduction unit which introduces, into the second chamber, second gaswhich generates hydroxyl radicals by being turned into plasma, and asecond plasma generation unit which turns the second gas into plasma andto which a second DC voltage higher than the first DC voltage isapplied.

A laminate body of the present application includes a resin base memberin which a part of atoms present on a hydrophobic surface of resin isreplaced with a hydroxyl group, and a metal deposition film formed on asurface of the resin base member. Here, a contact angle of the surfaceof the resin base member with water is equal to or smaller than 30°.

Effect of the Invention

According to the resin surface hydrophilization method of the presentapplication, high hydrophilicity can be imparted to a hydrophobicsurface of resin for a long period of time. Therefore, a metal film iseasily formed on the surface of resin. According to the laminate bodymanufacturing method of the present application, a laminate body inwhich a resin base member and a metal deposition film are brought firmlyclose contact with each other can be obtained. According to the plasmaprocessing device of the present application, the resin surfacehydrophilization method of the present application can be easilyperformed. In the laminate body of the present application, a resin basemember and a metal deposition film are brought into firmly close contactwith each other.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flow of a laminate body manufacturing method.

FIG. 2 is a schematic cross-sectional view showing a basic configurationof a processing device.

FIG. 3 is a schematic cross-sectional view of a plasma processing deviceaccording to a first embodiment.

FIG. 4 is a schematic cross-sectional view of the plasma processingdevice according to a second embodiment.

FIG. 5 is a schematic cross-sectional view of the plasma processingdevice according to a third embodiment.

FIG. 6 is a schematic vertical cross-sectional view of the plasmaprocessing device according to a fourth embodiment.

FIG. 7 is a schematic horizontal cross-sectional view of the plasmaprocessing device according to the fourth embodiment.

FIGS. 8A to 8D show images when water was dropped on a surface of asubstrate before and after processing of an example, and SEM images ofthe surface of the substrate.

FIG. 9 is a graph showing the measurement results of contact angles ofthe surface of the substrate after the processing of the embodiment withwater.

DETAILED DESCRIPTION

In order to apply resin to an electronic substrate or the like, it isnecessary to hydrophilize a hydrophobic surface of the resin. FIG. 1shows a flow of each step of a laminate body manufacturing method of thepresent application. In the laminate body manufacturing method, thefirst two steps correspond to a resin surface hydrophilization method.That is, the resin surface hydrophilization method of the embodiments ofthe present application includes a desorption step S10 and anintroduction step S20. In the desorption step S10, a hydrophobic surfaceof resin is irradiated with plasma to desorb at least some of the atomsconstituting the resin from the surface of the resin. That is, in thedesorption step S10, the hydrophobic surface of the resin is cleanedwith the plasma, in particular, with ions in the plasma to activate thesurface of the resin.

The resin is not particularly limited as long as it has a hydrophobicsurface, and examples thereof include fluororesin such as PTFE,polyimide, and LCP. It is preferable that the resin contains fluorineand carbon and that the atom desorbing from the hydrophobic surface ofthe resin is fluorine and carbon. This is because the hydrophobicsurface of the resin is largely hydrophilized. In addition, the resincontaining fluorine has a high insulating property and is excellent asan electronic substrate. The resin may contain wholly aromaticpolyester, and the atom desorbing from the hydrophobic surface of theresin may be oxygen. It is preferable that the plasma contains at leastone of nitrogen and argon. This is because atoms constituting the resinare easily desorbed from the surface of the resin by ions of nitrogen orargon.

In the introduction step S20, the surface of the resin subjected to thedesorption step S10 is irradiated with hydroxyl radicals to introduce ahydroxyl group (—OH) onto the surface of the resin. The surface of theresin into which the hydroxyl group is introduced has highhydrophilicity. For example, water vapor is turned into plasma, and thesurface of the resin subjected to the desorption step S10 is irradiatedwith hydroxyl radicals in the plasma. It is preferable that thedesorption step S10 and the introduction step S20 are performed in areduced pressure state, and that the introduction step S20 is performedafter the desorption step S10 while the reduced pressure state ismaintained. This is because a hydroxyl group can be introduced into thesurface of the resin while maintaining a state in which the surface ofthe resin is activated in the desorption step S10. The surface of theresin subjected to the introduction step S20 maintains hydrophilicityover a long period of time, for example, one month or more. Therefore,there is no problem even when the resin is opened to the atmosphereafter the introduction step S20.

It is preferable that the desorption step S10 is performed at a firstpressure equal to or higher than 0.1 Pa and equal to or lower than 0.4Pa, and the introduction step S20 is performed at a second pressureequal to or higher than 30% and equal to or lower than 50% of the firstpressure. This is because, in the desorption step S10, the progressmethod of ions and radicals in the plasma is easily controlled, and inthe introduction step S20, the surface of the resin is hardly irradiatedwith ions and easily irradiated with hydroxyl radicals. The introductionstep S20 is preferably performed at a temperature of the resin beingequal to or higher than 150° C. and equal to or lower than 300° C. Thisis because the chemical reaction between the hydroxyl group and thesurface of the resin is promoted, and the hydroxyl group is firmlyintroduced into the surface of the resin.

When the resin obtained with the resin surface hydrophilization methodso far is used for an electronic substrate, it is desirable to attach ametal, for example, copper to the surface of the resin. Therefore, themetal target is irradiated with plasma, ions, or radicals, and the metalejected from the metal target is thinly deposited on the surface of theresin. That is, the laminate body manufacturing method of the presentapplication includes the desorption step S10, the introduction step S20,and a deposition step S30. In other words, the laminate bodymanufacturing method of the present application includes the depositionstep S30 after the resin surface hydrophilization method of the presentapplication. Since the desorption step S10 and the introduction step S20are the same as those in the resin surface hydrophilization method ofthe present application, the description of the desorption step S10 andthe introduction step S20 is omitted.

In the deposition step S30, a metal film is deposited on the surface ofthe resin subjected to the introduction step S20. The deposition of themetal film is performed by, for example, a CVD method or a PVD method(sputtering). Examples of the metal film include a copper film, a silverfilm, and a gold film. In the deposition step S30, the resin opened tothe atmosphere after the introduction step S20 may be used. However, inorder to improve productivity and to suppress various contaminants fromadhering to the resin, it is preferable to perform the introduction stepS20 and the deposition step S30 while maintaining the reduced pressurestate.

On the surface of the deposited metal film, plating or thermocompressionbonding of the same metal is easily performed. That is, the laminatebody manufacturing method of the present application may further includea coating step S40 after the deposition step S30. In the coating stepS40, the surface of the deposited metal film is further coated with ametal layer formed of the same metal as the metal forming the metalfilm. Examples of the method of coating the surface of the metal filmwith the metal layer include a method in which the metal film and themetal layer of the laminate body subjected to the deposition step S30are bonded together by thermocompression bonding, and a method in whichthe metal layer is formed on the metal film of the laminate bodysubjected to the deposition step S30 by plating.

The laminate body of the embodiments of the present application includesthe resin base member in which a part of atoms present on thehydrophobic surface of the resin is replaced with a hydroxyl group, andthe metal deposition film formed on the surface of the resin basemember. Then, the contact angle of the surface of the resin base memberwith water is equal to or smaller than 30°. Therefore, the surface ofthe resin base member and the metal deposition film are brought intofirmly close contact with each other. More preferably, the contact angleof the surface of the resin base member with water is equal to orsmaller than 10°. The laminate body of the present application mayfurther include, on the surface of the metal deposition film, the metallayer composed of the same metal as the metal forming the metaldeposition film. The resin may be polytetrafluoroethylene, and the atomreplaced with a hydroxyl group may be fluorine. Further, the resin maybe liquid crystal polymer containing wholly aromatic polyester.

FIG. 2 shows the basic configuration of a processing device 80 which canbe used in the resin surface hydrophilization method of the presentapplication. The processing device 80 includes a vacuum chamber 2, afine plasma gun (FPG) 3 as the “plasma irradiation source”, a holdingbase 4, a cover 5, a first DC power source 9, and a second DC powersource 8. The vacuum chamber 2 is made of a metal such as aluminum alloyor stainless steel and is connected to the ground 10. The FPG 3 isarranged at the upper part in the vacuum chamber 2. The FPG 3 turnsprocessing gas introduced into the vacuum chamber 2 from a gasintroduction unit (not shown) into plasma.

As the FPG 3, for example, one described in International PublicationNo. 2014/175702 can be adopted. The holding base 4 is installed belowthe FPG 3 to face the FPG 3. The holding base 4 is made of metal or anelectrode, and holds a to-be-processed member 1. The cover 5 covers theupper surface of the holding base 4. The cover 5 is made of the samematerial as the to-be-processed member 1 so that the to-be-processedmember 1 is uniformly irradiated with the plasma from the FPG 3. Thefirst DC power source 9 is connected to the holding base 4. The secondDC power source 8 is connected to the FPG 3.

The processing gas such as nitrogen, argon, oxygen, and water vapor isintroduced into the vacuum chamber 2 from the gas introduction unitwhile depressurizing the vacuum chamber 2 by an exhaust pump (notshown), thereby adjusting the pressure in the vacuum chamber 2 to apredetermined value, for example, 0.3 Pa being in a range between 0.1 Paand 0.4 Pa both inclusive. In this state, when a second DC voltage isapplied to the FPG 3 from the second DC power source 8, the plasma isgenerated from the processing gas in the FPG 3.

At this time, if the pressure in the vacuum chamber 2 is too high, forexample, when the pressure exceeds 0.4 Pa, the processing gas becomesinto a glow discharge state, and the travel direction of ions 7 andradicals 6 in the plasma cannot be controlled. On the other hand, whenthe pressure in the vacuum chamber 2 is within an appropriate range, adark discharge state of the processing gas can be maintained, and thetravel direction of the ions 7 and the radicals 6 can be controlled.Therefore, the pressure in the vacuum chamber 2 is adjusted to, forexample, a pressure equal to or higher than 0.1 Pa and equal to or lowerthan 0.4 Pa.

When the desorption step S10 is performed using the processing device80, the desorption step S10 is performed as the following procedure.First, the to-be-processed member 1 made of resin is held by the holdingbase 4, nitrogen and/or argon as the processing gas is introduced intothe vacuum chamber 2 from the gas introduction unit, and the pressure inthe vacuum chamber 2 is adjusted to 0.3 Pa being in a range between 0.1Pa and 0.4 Pa both inclusive by the exhaust pump. Next, the second DCpower source 8 is turned on while the first DC power source 9 is keptoff, that is, while the holding base 4 is grounded.

The plasma is generated from the processing gas in the FPG 3, and theto-be-processed member 1 is irradiated with the directional ions andradicals. Then, atoms are desorbed from the surface of theto-be-processed member 1 mainly by the impact of the ions. Since theions and radicals are directional, atoms can be efficiently desorbedfrom the surface of the to-be-processed member 1. Most of the desorbedatoms are discharged to the outside of the vacuum chamber 2 by theexhaust pump. Some of the desorbed atoms float in the vacuum chamber 2or adhere to an inner wall of the vacuum chamber 2 or a component in thevacuum chamber 2 after floating. However, in the present embodiment,since the pressure in the vacuum chamber 2 is lower than that in ageneral glow discharge condition, there is almost no impurity floatingin the vacuum chamber 2. Therefore, contamination of the to-be-processedmember 1 is suppressed.

When the desorption step S10 is performed using the processing device80, if the voltage of the second DC power source 8 is increased, alarger amount of the plasma is generated from the processing gas and thedesorption of atoms from the surface of the to-be-processed member 1 ispromoted. However, when the processing is performed at a high voltage atone time, the wrinkled wall shown in the photograph of FIG. 8B grows toomuch and the unevenness becomes large. Large unevenness is undesirableto cause increasing of the transmission loss of the electronicsubstrate. In the present invention, the voltage of the second DC powersource 8 is changed with time. Since the unevenness is not formed at thebeginning of the desorption step S10, processing is performed at a highvoltage to have an increased desorption amount. By processing at a highvoltage, contaminants adhering to the surface of the to-be-processedmember 1 can also be preferably removed at once. When wrinkles areformed and unevenness is generated, the voltage is lowered and mildprocessing is performed so that the surface roughness is notdeteriorated. Although residual stress is generated on the surface bythe processing, the residual stress can be suppressed by mild processingin which the voltage is lowered in the latter half process.

When the introduction step S20 is performed using the processing device80, the introduction step S20 is performed as the following procedure.Note that the desorption step S10 and the introduction step S20 arepreferably performed by separate processing devices 80. This is becausewhen the introduction step S20 is performed in the same processingdevice 80 as the processing device 80 in which the desorption step S10has been performed, that is, when the introduction step S20 is performedafter the desorption step S10 in the same processing device 80,components desorbed from the surface of the to-be-processed member 1 inthe desorption step S10 may adhere to the inside of the vacuum chamber2, and in the subsequent introduction step S20, the adhering substancesmay float and adhere to the surface of the to-be-processed member 1. Ifthere is no influence of the floating substances derived from thedesorption step S10, the desorption step S10 and the introduction stepS20 may be performed in the same processing device 80

First, the to-be-processed member 1 subjected to the desorption step S10is held by the holding base 4. It is preferable that the to-be-processedmember 1 is moved from the processing device 80 in which the desorptionstep S10 is performed to the processing device 80 in which theintroduction step S20 is to be performed without being opened to theatmosphere, for example, by providing a vacuum preliminary chamberbetween the two processing devices 80. Next, the processing gascontaining water and/or water vapor is introduced into the vacuumchamber 2 from the gas introduction unit. It is preferable that theprocessing gas is water vapor. This is because hydroxyl radicals areeasily generated as the radicals 6.

Then, the pressure in the vacuum chamber 2 is adjusted by the exhaustpump so that the pressure in the vacuum chamber 2 becomes equal to orhigher than 30% and equal to or lower than 50% of the pressure in thedesorption step S10. Since the pressure in the introduction step S20 isequal to or higher than 30% and equal to or lower than 50% of thepressure in the desorption step S10, a large amount of hydroxyl radicalsare generated as the radicals 6 in the plasma from the processing gas.Next, the first DC power source 9 and the second DC power source 8 areturned on. The plasma is generated from the processing gas by apotential difference between the FPG 3 and the grounded vacuum chamber2.

At this time, the voltage from the first DC power source 9 is preferablysmaller than the voltage from the second DC power source 8, and is morepreferably smaller than the voltage from the second DC power source 8 asbeing equal to or higher than 40% of the voltage from the second DCpower source 8. This is because, by reducing the potential differencebetween the FPG 3 and the holding base 4, a large amount of hydroxylradicals can be extracted as the radicals 6 from the plasma from theprocessing gas and the to-be-processed member 1 can be irradiatedtherewith. That is, since the vacuum chamber 2 is grounded, thepotential difference between the FPG 3 and the vacuum chamber 2 islarger than the potential difference between the FPG 3 and the holdingbase 4. Accordingly, most of the ions 7 in the plasma from theprocessing gas move not in the direction from FPG 3 to the holding base4 but in the direction from the FPG 3 to the vacuum chamber 2. Theto-be-processed member 1 is irradiated with the hydroxyl radicals as theradicals 6, which have no polarity in the remaining plasma.

Owing to that the to-be-processed member 1 is irradiated with thehydroxyl radicals as the radicals 6, the hydroxyl group is introducedinto the surface of the to-be-processed member 1. In addition, since theto-be-processed member 1 is hardly irradiated with the ions 7, it ispossible to suppress the hydroxyl group introduced into the surface ofthe to-be-processed member 1 by the impact of the ions from beingdesorbed again. Thus, stable hydrophilicity is imparted to the surfaceof the to-be-processed member 1. By introducing the hydroxyl group, thehydroxyl group is chemically bonded to the surface of theto-be-processed member 1.

FIG. 3 schematically shows a plasma processing device 90 of the firstembodiment of the present application. In the first embodiment, theto-be-processed member is a sheet-like resin. The plasma processingdevice 90 includes a first processing device 91 and a second processingdevice 92. The first processing device 91 for performing the desorptionstep S10 includes a first chamber 25, a supply roller 11, first holdingunits 14, 15, a first gas introduction unit 17, and FPGs 12, 13 as a“first plasma generation unit” and a “plasma irradiation source.”

The supply roller 11 is wound with a sheet-like resin having ahydrophobic surface, and supplies the resin to the first holding units14, 15 while rotating. The resin supplied from the supply roller 11 isheld while being wound around a part of the cylindrical first holdingunits 14, 15. The FPGs 12 are arranged so as to face the first holdingunit 14. The FPGs 13 are arranged so as to face the first holding unit15. With such an arrangement of the first holding units 14, 15 and theFPGs 12, 13, the desorption step S10 can be performed on both surfacesof the resin in the first processing device 91. Further, since two FPGsare arranged for one first holding unit, the desorption step S10 can beefficiently performed.

The first gas introduction unit 17 introduces first gas to desorb, whenturned into plasma, at least some of the atoms constituting the resinfrom the surface of the resin into the first chamber 25. In other words,when the first gas is turned into plasma, ions and radicals havingdirectionality in the plasma act on the surface of the resin, so that atleast some of the atoms constituting the resin is desorbed from thesurface of the resin. In the first embodiment, the first gas is nitrogenand/or argon.

A voltage is applied to each of the FPGs 12, 13 from a power source (notshown) to cause the first gas to turn into plasma. No voltage is appliedto the first holding units 14, 15. That is, the first holding units 14,15 are grounded. A plasma generating means in the first plasmageneration unit is not particularly limited. The first plasma generationunit may generate plasma by being applied with an AC voltage. Thepressure in the first chamber 25 is about 0.3 Pa at which dark dischargecan be maintained.

In the desorption step S10, if the voltage of the FPGs 12, 13 isincreased, a larger amount of the plasma is generated from theprocessing gas and the desorption of atoms from the surface of theto-be-processed member 1 is promoted. However, when the processing isperformed at a high voltage at one time, the wrinkled wall shown in thephotograph of FIG. 8B grows too much and the unevenness becomes large.Large unevenness is undesirable to cause increasing of the transmissionloss of the electronic substrate. In the present invention, the levelsof the voltages to be applied to the respective FPGs 12, 13 are setbased on the order in which the sheet of the to-be-processed member 1 isirradiated with the plasma. More specifically, among the two FPGs 12 aswell as among the two FPGs 13, a difference is provided between thevoltage to be applied to the FPG antecedently performing irradiationonto the sheet of the to-be-processed member 1 and the voltage to beapplied to the FPG subsequently performing irradiation onto the sheet.The levels of the voltages to be applied to the respective FPGs 12, 13are set based on the order in which the to-be-processed member 1 isirradiated with plasma.

For example, in FIG. 3, for the FPGs 12, 13 causing the sheet of theto-be-processed member 1 to be antecedently irradiated with the plasma(i.e., the FPG 12 and the FPG 13 each located on the left side in FIG.3), since unevenness is not formed at the start of the desorption step,the voltage to be applied thereto is set to a high voltage. Byprocessing at a high voltage, contaminants adhering to the surface canalso be preferably removed at once. On the other hand, for the FPGs 12,13 causing the sheet of the to-be-processed member 1 to be subsequentlyirradiated with the plasma (i.e., the FPG 12 and the FPG 13 each locatedon the right side in FIG. 3), since unevenness is formed due to thegenerated wrinkles, a voltage lower than that for the FPGs 12, 13causing the sheet to be antecedently irradiated with the plasma (i.e.,the FPG 12 and the FPG 13 each located on the left side in FIG. 3) isapplied thereto so that mild processing is performed. Although residualstress is generated on the surface by the processing, owing to that themild processing is performed due to plasma irradiation onto theto-be-processed member 1 by the FPGs 12, 13 causing the subsequentplasma irradiation (the FPGs 12, 13 each located on the right side inFIG. 3), it is also possible to suppress the residual stress.

A resin 16 a having passed through the first holding unit 14 has onesurface processed. Thereafter, when the resin 16 a passes through thefirst holding unit 15, a resin 16 b having both surfaces processed isobtained. The resin 16 b having both surfaces processed is wound arounda part of the guide roller 19. When the resin is fluororesin such asPTFE, both surfaces of the resin 16 b are activated by desorption offluorine and/or carbon. When the resin is wholly aromatic polyester,both surfaces of the resin 16 b are activated by desorption of oxygen.The resin 16 b is supplied via the guide roller 19 into a second chamber27 of the second processing device 92 which performs the introductionstep S20 in a state in which both surfaces thereof are activated.

A connection portion 26 provided with differential exhaust is arrangedbetween the first chamber 25 and the second chamber 27. The differentialexhaust separates the first chamber 25 and the second chamber 27 and thepressure in the first chamber 25 and the pressure in the second chamber27 can be set different. As described above, since the desorption stepS10 and the introduction step S20 are continuously performed byseparately using the first processing device 91 and the secondprocessing device 92, high productivity can be ensured.

The second processing device 92 for performing the introduction step S20includes the second chamber 27, second holding units 22, 23, a secondgas introduction unit 18, and FPGs 20, 21 as the “second plasmagenerating unit” and the “plasma irradiation source.” The second chamber27 is grounded. The second holding units 22, 23 hold the resin 16 bprocessed in the first chamber 25, and a first DC voltage is appliedfrom a power source (not shown). Each of the second holding units 22, 23include a heater 28 serving as a heating unit. The temperature of thesecond holding units 22, 23 is preferably maintained at a temperatureequal to or higher than 150° C. and equal to or lower than 300° C. bythe heaters 28. This is because a hydroxyl group can be efficientlyintroduced into the surface of the resin 16 b.

The second gas introduction unit 18 introduces, into the second chamber27, a second gas which is turned into plasma to generate hydroxylradicals. In the first embodiment, the second gas is water vapor. TheFPGs 20, 21 turn the second gas into plasma, and a second DC voltagehigher than the first DC voltage is applied from a power source (notshown). For example, the first DC voltage is equal to or larger than 40%and equal to or lower than 99% of the second DC voltage. The resin 16 bsupplied from the first chamber 25 is held while being wound around apart of the cylindrical second holding units 22, 23.

The FPGs 20 are arranged so as to face the second holding unit 22. TheFPGs 21 are arranged so as to face the second holding unit 23. With suchan arrangement of the second holding units 22, 23 and the FPGs 20, 21,the introduction step S20 can be performed on both surfaces of the resinin the second processing device 92. Further, since two FPGs are arrangedfor one second holding unit, the introduction step S20 can beefficiently performed. In order to facilitate the introduction of ahydroxyl group into the surfaces of the resin 16 b in the introductionstep S20, the pressure in the second chamber 27 is preferably equal toor higher than 30% and equal to or lower than 50% of the pressure in thefirst chamber 25.

At the potential difference between the FPGs 20, 21 and the secondchamber 27, plasma of the second gas is generated and ions such ashydrogen ions and hydroxyl radicals are generated. A resin 16 c havingpassed through the second holding unit 22 is hydrophilized on onesurface thereof. A resin 16 d having passed through the second holdingunit 23 is hydrophilized on both surfaces thereof. The resin 16 d iswound to a winding roller 24. After the surfaces of all the resin arehydrophilized, the second chamber 27 is opened to the atmosphere and theresin 16 d is taken out.

FIG. 4 schematically shows a plasma processing device 95 of a secondembodiment of the present application. The plasma processing device 95includes a first processing device (not shown), a second processingdevice 93, and a third processing device 96 which performs thedeposition step S30. The second processing device 93 is substantiallythe same as the second processing device 92. The third processing device96 includes a third chamber 65, third holding units 68, 71, and metaldeposition units 97 98. The third holding units 68, 71 hold the resin 16d processed in the second chamber 27.

Each of the metal deposition units 97, 98 deposits metal on acorresponding surface of the resin 16 d held by the third holding units68, 71. The metal deposition unit 97 includes an FPG 67 as the “plasmairradiation source” and a copper target 66 serving as a metal target.That is, an ion beam emitted from the FPG 67 collides with the coppertarget 66, and copper ejected from the copper target 66 is deposited onone surface of the resin 16 d to form a copper deposition film. Thethickness of the copper deposition film is equal to or larger than 10 nmand equal to or smaller than 400 nm. Further, the metal deposition unit98 includes an FPG 70 as the “plasma irradiation source” and a coppertarget 69.

The resin 16 d subjected to the introduction step S20 in the secondchamber 27 is supplied into the third chamber 65 via the guide roller63. A connection portion 64 provided with differential exhaust isarranged between the second chamber 27 and the third chamber 65. Theresin 16 d supplied into the third chamber 65 is held while being woundaround a part of the cylindrical third holding units 68, 71. When theresin 16 d passes through the third holding unit 68, a laminate body 62b in which the copper deposition film is formed on one surface of theresin 16 d is obtained.

Thereafter, when the laminate body 62 b passes through the third holdingunit 71, a laminate body 62 c in which the copper deposition films areformed on both sides of the resin 16 d is obtained. The laminate body 62c is wound to the winding roller 24. After the copper deposition filmsare formed on both surfaces of all the resin 16 d, the third chamber 65is opened to the atmosphere and the laminate body 62 c is taken out. Itis preferable that the processes from the desorption step S10 to thedeposition step S30 are continuously performed under reduced pressure.

Since ions in the plasma of the second gas collide with the inner wallof the second chamber 27 of the first embodiment and the vicinitythereof, metals contained in the inner wall and components installedinside the second chamber 27 float from the inner wall of the secondchamber 27 and the components. Some of the floating metal may adhere tothe resins 16 b, 16 c, 16 d. Therefore, it is preferable that at least apart of the inner wall of the second chamber 27, the FPGs 20, 21 servingas the plasma generation unit, and the components installed in thesecond chamber 27, to be in contact with the plasma, is made of the samemetal as that to be deposited in the third processing device, forexample, copper, gold, or silver. This is because the metal deposited bythe third processing apparatus is the same as at least a part of theinner wall of the second chamber 27, the FPGs 20, 21, and the componentsinstalled in the second chamber 27, so as not to be defective even whenthe metal floating from the inner wall of the second chamber 27, theFPGs 20, 21, and the components installed in the second chamber 27adheres to the resins 16 b, 16 c, 16 d.

Further, as in a plasma processing device 100 of a third embodimentshown in FIG. 5, sheets 50, 51 made of the same metal as the metal to bedeposited by the third processing device may be arranged as a shieldingportion for covering at least a part of the inner wall of the secondchamber 27 of the second processing device 101 and the componentsinstalled in the second chamber 27, for example, the FPGs 20, 21. Sincethe metal deposited by the third processing device is the same as themetal forming the sheets 50, 51, it is prevented from being defectiveeven when the metal floating from the sheets 50, 51 adheres to theresins 16 b, 16 c, 16 d.

FIGS. 6 and 7 schematically show a plasma processing device 110 of afourth embodiment of the present application. In the fourth embodiment,the to-be-processed member is a resin 30 a in the form of a sheet-likepiece. The plasma processing device 110 includes vacuum preliminarychambers 38, 41, a first processing chamber 111 for performing thedesorption step S10, a second processing chamber 112 for performing theintroduction step S20, and gate valves 33, 34, 35, 36, 37. The firstprocessing chamber 111 includes a first chamber 39. The secondprocessing chamber 112 includes second chambers 40 a, 40 b.

As shown in FIG. 7, a movable portion 31 for holding the resin 30 a atthe end thereof and a raceway portion 32 a for mounting and conveyingthe movable portion 31 are arranged in the vacuum preliminary chamber38. Similarly, a raceway portion 32 b for conveying the movable portion31 holding the resin 30 b is arranged in the first chamber 39. Further,a raceway portion 32 c for conveying the movable portion 31 holding theresin 30 c is arranged in the second chamber 40 a. Further, a racewayportion 32 d for conveying the movable portion 31 holding the resin 30 dis arranged in the second chamber 40 b. Further, a raceway portion 32 efor conveying the movable portion 31 holding the resin 30 e is arrangedin the vacuum preliminary chamber 41. A linear guide, a rack-and-pinion,or the like can be adopted as a conveying method for the resins 30 a, 30b, 30 c, 30 d, 30 e.

The plasma processing device 110 is operated as follows. The gate valve33 is opened, and the movable portion 31 holding the end part of theresin 30 a is mounted on the raceway portion 32 a in the vacuumpreliminary chamber 38. The gate valve 33 is closed to reduce thepressure in the vacuum preliminary chamber 38. When the pressure in thevacuum preliminary chamber 38 becomes equal to or lower than 10 Pa, thegate valve 34 is opened. The movable portion 31 is moved into the firstchamber 39 and the gate valve 34 is closed. Using the FPGs 42, 43 as the“plasma irradiation source”, the desorption step S10 is performed on theresin 30 b in the first chamber 39 to obtain the resin 30 c having bothsurfaces thereof activated. At this time, the resin 30 b can beefficiently and homogeneously processed while using two pairs of theFPGs 42, 43.

When the desorption step S10 is completed, the resin 30 c, that is, themovable portion 31 moves to the position in front of the gate valve 35.The gate valve 35 is opened to move the movable portion 31 into thesecond chamber 40 a and the gate valve 35 is closed. In the secondchamber 40 a, the introduction step S20 is performed on the uppersurface of the resin 30 c to obtain the resin 30 d. The resin 30 d, thatis, the movable portion 31 moves to the position in front of the secondchamber 40 b. In the second chamber 40 b, the introduction step S20 isperformed on the lower surface of the resin 30 d to obtain the resin 30e. At this time, the voltage applied to an electrode plate 45 a islarger than the voltage of the grounded second chamber 40 a and smallerthan the voltage applied to the FPG 44 a as the “plasma radiationsource.” At this time, the voltage applied to an electrode plate 45 b islarger than the voltage of the grounded second chamber 40 b and smallerthan the voltage applied to the FPG 44 b as the “plasma radiationsource.”

Accordingly, most of the ions in the plasma from the processing gas movenot in the direction from the FPGs 44 a, 44 b to the electrode plates 45a, 45 b but in the direction from the FPGs 44 a, 44 b to the secondchambers 40 a, 40 b. The resins 30 c, 30 d are irradiated with theremaining hydroxyl radicals in the plasma. The resin 30 e, that is, themovable portion 31 moves to the position in front of the gate valve 36.The gate valve 36 is opened, the movable portion 31 is moved into thevacuum preliminary chamber 41, and the gate valve 36 is closed. Afterthe pressure in the vacuum preliminary chamber 41 is made atmospheric,the gate valve 37 is opened to take out the resin 30 e.

Examples

(Desorption Step)

In a grounded stainless steel chamber, fine plasma guns (FPG) (lineartype ion beam source FPG-L040S manufactured by Finesolution Co., Ltd.)(the same applies hereinafter) were used to perform the desorption stepon a commercially available A4-grade fluororesin substrate under theconditions that the pressure in the chamber was 0.3 Pa, the electricpower supplied to the FPG was 300 W, and the processing gas was nitrogenor argon.

(Introduction Step)

In a grounded stainless steel chamber, fine plasma guns (FPG) were usedto perform the introduction step on the substrate subjected to thedesorption step while the voltage applied to the holding base holdingthe substrate was set lower than the voltage applied to the FPG underthe conditions that the pressure in the chamber was 0.15 Pa in thechamber, the electric power supplied to the FPG was 300 W, and theprocessing gas was water vapor.

FIG. 8A shows an image obtained by measuring the contact angle of thesurface of the substrate with water without performing the desorptionstep and the introduction step, that is, before the processing. As shownin FIG. 8A, the water dropped on the surface of the substrate before theprocessing was rounded. In other words, the surface of the substratebefore the processing exhibited high water repellency. The contact angleof the surface of the substrate before the processing with water waslarger than 90°. Further, FIG. 8B shows an image obtained by measuringthe contact angle of the surface of the substrate with water afterperforming the desorption step and the introduction step, that is, afterthe processing. As shown in FIG. 8B, the water dropped on the surface ofthe substrate after the processing spread. In other words, the surfaceof the substrate after the processing exhibited high waterhydrophilicity.

FIG. 8C shows a scanning electron microscope (SEM) image of the surfaceof the substrate before the processing. Scratches and holes generatedwhen the fluororesin block was peeled off into a sheet shape wereobserved. FIG. 8D shows an SEM image of the surface of the substrateafter the processing. The scratches and holes observed on the surface ofthe substrate before the processing disappeared, and elongatedunevenness was observed. The unevenness is considered to be caused bythe irradiation of the substrate with ions in the desorption step. Asdescribed above, although the surface morphology of the substratechanged greatly before and after the processing, the surface roughnessof the substrate hardly changed before and after the processing.

FIG. 9 shows the measurement result of the contact angle of the surfaceof the fluororesin sheet after the processing with water. The short sideof the fluororesin sheet was taken as an X axis, the long side was takenas a Y axis, and the center of the fluororesin sheet was taken as acoordinate (0,0). The contact angle with water was measured at a totalof 15 points including 5 points in the short side direction and 3 pointsin the long side direction. One point was measured twice and the meanvalue was plotted. The variation in the Y-axis direction was 0.3° to1.9° at any X-axis point. Further, the variation in the X-axis directionwas 1.6° to 1.9°. The contact angle was smaller than 6° at allmeasurement points. When the surface of the substrate after theprocessing was directly plated with copper, the degree of adhesionbetween the substrate and the copper was about 0.8 N/mm, indicatingstrong adhesion between the substrate and the copper.

INDUSTRIAL APPLICABILITY

The resin surface hydrophilization method, the plasma processing device,the laminate body, and the laminate body manufacturing method of thepresent application are used for a circuit substrate used in a mobilephone for communicating high-speed and large-capacity information. Sincethe relative dielectric constant of the fluororesin is lower than thatof air, the fluororesin substrate is particularly suitable for amaterial of a high-frequency substrate. Compared with circuit substratesusing other general materials, a circuit substrate using fluororesin hasa low relative dielectric constant and small dielectric loss tangenteven when a high frequency current flows, and has a small dielectricloss.

When the resin surface hydrophilization method of the presentapplication is applied to a fluororesin substrate, the hydrophilicity ofthe substrate is improved, the adhesion with copper wiring can beimproved, and a circuit substrate which can withstand use in a highfrequency band can be provided. The technology applicable to the use inthe high frequency band can be applied not only to the main body of themobile phone but also to a substrate used for a base station of themobile phone, a substrate for communication dedicated to a home, afactory, or an area, or a substrate for a millimeter wave radar used forautomatic driving of an automobile, a drone, or the like, and has a wideapplication range.

REFERENCE SIGNS LIST

-   S10 Desorption step-   S20 Introduction step-   S30 Deposition step-   S40 Coating step-   1 To-be-processed member-   2 Vacuum chamber-   3, 12, 13, 20, 21, 42, 43, 44 a, 44 b, 67, 70 Fine plasma gun (FPG,    Plasma irradiation source)-   4 Holding base-   5 Cover-   6 Radical (Hydroxyl radical)-   7 Ion-   8 Second DC power source-   9 First DC power source-   10 Ground-   11 Supply roller-   14, 15 First holding unit-   16 a, 16 b, 16 c, 16 d, 30 a, 30 b, 30 c, 30 d, 30 e Resin-   17 First gas introduction unit-   18 Second gas introduction unit-   19 Guide roller-   22, 23 Second holding unit-   24 Winding roller-   25, 39 First chamber-   31 Movable portion-   32 a, 32 b, 32 c, 32 d, 32 e Raceway portion-   33, 34, 35, 36, 37 Gate valve-   38, 41 Vacuum preliminary chamber-   45 a, 45 b Electrode plate-   62 b, 62 c Laminate body-   65 Third chamber-   68, 71 Third holding unit-   66, 69 Copper target-   80 Processing device-   90, 95, 100, 110 Plasma processing device-   91, 111 First processing device-   92, 93, 101, 112 Second processing device-   96 Third processing device-   97, 98 Metal deposition unit

1. A resin surface hydrophilization method, comprising: a desorptionstep of desorbing at least a part of atoms constituting resin from ahydrophobic surface of the resin by irradiating the surface with plasma;and an introduction step of introducing a hydroxyl group on the surfaceof the resin subjected to the desorption step by irradiating the surfaceof the resin with hydroxyl radicals, wherein the desorption step isperformed at a first pressure equal to or higher than 0.1 Pa and equalto or lower than 0.4 Pa, and the introduction step is performed at asecond pressure equal to or higher than 30% and equal to or lower than50% of the first pressure.
 2. The resin surface hydrophilization methodaccording to claim 1, wherein the resin contains fluorine and carbon,and the atoms are fluorine and carbon.
 3. The resin surfacehydrophilization method according to claim 1, wherein the resin containswholly aromatic polyester and the atoms are oxygen.
 4. The resin surfacehydrophilization method according to claim 1, wherein gas for generatingthe plasma contains at least one of nitrogen and argon, the desorptionstep and the introduction step are performed in a reduced pressurestate, and the introduction step is performed after the desorption stepwhile the reduced pressure state is maintained.
 5. (canceled)
 6. Theresin surface hydrophilization method according to claim 1, wherein avoltage applied to a plasma irradiation source in the desorption step isset to change with time.
 7. The resin surface hydrophilization methodaccording to claim 1, wherein a plurality of plasma irradiation sourcesare used in the desorption step, and voltages applied to the respectiveplasma irradiation sources are set to change in relation to the order inwhich the resin to be processed is irradiated.
 8. The resin surfacehydrophilization method according to claim 1, wherein the introductionstep is performed at a temperature of the resin being equal to or higherthan 150° C. and equal to or lower than 300° C.
 9. A laminate bodymanufacturing method, comprising: a desorption step of desorbing atleast a part of atoms constituting resin from a hydrophobic surface ofthe resin by irradiating the surface with plasma; an introduction stepof introducing a hydroxyl group on the surface of the resin subjected tothe desorption step by irradiating the surface of the resin withhydroxyl radicals; and a deposition step of depositing a metal film on asurface of the resin subjected to the introduction step, wherein thedesorption step is performed at a first pressure equal to or higher than0.1 Pa and equal to or lower than 0.4 Pa, and the introduction step isperformed at a second pressure equal to or higher than 30% and equal toor lower than 50% of the first pressure.
 10. The laminate bodymanufacturing method according to claim 9, further comprising a coatingstep of coating a surface of the metal film with a metal layer formed ofthe same metal as the metal forming the metal film.
 11. A plasmaprocessing device, comprising: a first processing device including afirst chamber, a first holding unit which holds resin, a first gasintroduction unit which introduces, into the first chamber, first gasfor desorbing at least a part of atoms constituting the resin from asurface of the resin when turned into plasma, and a first plasmageneration unit which turns the first gas into plasma; and a secondprocessing device including a grounded second chamber, a second holdingunit which holds the resin processed in the first chamber and to which afirst DC voltage is applied, a second gas introduction unit whichintroduces, into the second chamber, second gas which generates hydroxylradicals by being turned into plasma, and a second plasma generationunit which turns the second gas into plasma and to which a second DCvoltage higher than the first DC voltage is applied.
 12. The plasmaprocessing device according to claim 11, wherein the second holding unitincludes a heating unit.
 13. The plasma processing device according toclaim 11, further comprising a third processing device including a thirdchamber, a third holding unit which holds the resin processed in thesecond chamber, and a metal deposition unit which deposits a metal onthe resin held by the third holding unit.
 14. The plasma processingdevice according to claim 13, wherein at least a part of an inner wallof the second chamber, the plasma generation unit, and componentsinstalled in the second chamber, to be in contact with the plasma, ismade of the same metal as the metal.
 15. A laminate body, comprising: aresin base member in which a part of atoms present on a hydrophobicsurface of resin is replaced with a hydroxyl group; and a metaldeposition film formed on a surface of the resin base member, wherein acontact angle of the surface of the resin base member with water isequal to or smaller than 30°.
 16. The laminate body according to claim15, wherein the resin is polytetrafluoroethylene and the atoms arefluorine, or the resin is liquid crystal polymer containing whollyaromatic polyester.